1. Field of the Invention
The present invention relates to a detector in which mass portions formed from a semiconductor through micro-machining and each having an inertial mass are excited in order to detect at least one physical quantity from among angular velocity, linear acceleration, and angular acceleration. More particularly, the present invention relates to a detector that has a detection axis perpendicular to a surface of a substrate and is effective in detection of angular velocity about an axis perpendicular to the detection axis and an excitation axis.
2. Description of the Related Art:
Japanese Patent Application Laid-Open (kokai) No. 2-218914 discloses a conventional angular velocity detector utilizing a Coriolis force. The angular velocity detector has a cruciform vibrator that has two X-axis vibration beams each extending along an +X axis and -X axis, respectively, and two Y-axis vibration beams each extending along a +Y axis and -Y axis, respectively. Through use of piezoelectric elements, the two X-axis vibration beams are vibrated in a positive direction along a Z axis perpendicular to a plane formed by the X-axis and Y-axis vibration beams, while the two Y-axis vibration beams are vibrated in a negative direction along the Z axis. Thus, angular velocity about the X axis is detected based on Y-axis reverse-phase vibration of the two X-axis vibration beams, and angular velocity about the Y axis is detected based on X-axis reverse-phase vibration of the two Y-axis vibration beams.
In the conventional angular velocity detector, since the vibration beams are excited along the Z axis perpendicular to the plane of the cruciform vibrator, vibration tends to leak from a supporting point at the center of the vibrator, resulting in a difficulty in obtaining stable vibration. Further, since the conventional angular velocity detector utilizes tuning fork vibrators and piezoelectric elements, the size of the detector cannot be decreased. Moreover, since wiring is required for supply of electricity to the piezoelectric elements, the state of vibration becomes unstable due to the wiring.